From 81fd0d6e265985213ec3d0c1db4b8a6f314481ea Mon Sep 17 00:00:00 2001
From: Maik Nijhuis <maik.nijhuis@triopsys.nl>
Date: Thu, 4 Aug 2022 16:09:20 +0200
Subject: ExternalProject: Fix install on BUILD_ALWAYS+BUILD_BYPRODUCTS with
 Ninja

The `BUILD_BYPRODUCTS` option causes the ExternalProject's `build` step
in `build.ninja` to have `restat = 1`, so its "always out-of-date"
status caused by `BUILD_ALWAYS` does not propagate to the `install`
step.  Mark the latter step as explicitly always out-of-date too.

Fixes: #23820
---
 Modules/ExternalProject.cmake                     | 14 ++++++++++++++
 Tests/RunCMake/ExternalProject/BUILD_ALWAYS.cmake |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/Modules/ExternalProject.cmake b/Modules/ExternalProject.cmake
index c7948cd..2520cf3 100644
--- a/Modules/ExternalProject.cmake
+++ b/Modules/ExternalProject.cmake
@@ -3829,6 +3829,19 @@ function(_ep_add_install_command name)
     set(uses_terminal "")
   endif()
 
+  # With BUILD_ALWAYS+BUILD_BYPRODUCTS, Ninja restats the
+  # build step outputs and may not consider this step to
+  # be out-of-date.  Explicitly mark it out-of-date too.
+  get_property(build_always
+    TARGET ${name}
+    PROPERTY _EP_BUILD_ALWAYS
+  )
+  if(build_always)
+    set(always 1)
+  else()
+    set(always 0)
+  endif()
+
   set(__cmdQuoted)
   foreach(__item IN LISTS cmd)
     string(APPEND __cmdQuoted " [==[${__item}]==]")
@@ -3839,6 +3852,7 @@ function(_ep_add_install_command name)
       COMMAND ${__cmdQuoted}
       WORKING_DIRECTORY \${binary_dir}
       DEPENDEES build
+      ALWAYS \${always}
       ${log}
       ${uses_terminal}
     )"
diff --git a/Tests/RunCMake/ExternalProject/BUILD_ALWAYS.cmake b/Tests/RunCMake/ExternalProject/BUILD_ALWAYS.cmake
index fdd3ad9..2e5fc6f 100644
--- a/Tests/RunCMake/ExternalProject/BUILD_ALWAYS.cmake
+++ b/Tests/RunCMake/ExternalProject/BUILD_ALWAYS.cmake
@@ -12,6 +12,9 @@ ExternalProject_Add(always
   DOWNLOAD_COMMAND ""
   CONFIGURE_COMMAND "${CMAKE_COMMAND}" -P ${CMAKE_CURRENT_BINARY_DIR}/always-configure.cmake
   BUILD_COMMAND "${CMAKE_COMMAND}" -P ${CMAKE_CURRENT_BINARY_DIR}/always-build.cmake
+        COMMAND "${CMAKE_COMMAND}" -E copy_if_different ${CMAKE_CURRENT_LIST_FILE}
+                   "${CMAKE_CURRENT_BINARY_DIR}/byproduct.txt"
+  BUILD_BYPRODUCTS "${CMAKE_CURRENT_BINARY_DIR}/byproduct.txt"
   BUILD_ALWAYS 1
   INSTALL_COMMAND "${CMAKE_COMMAND}" -P ${CMAKE_CURRENT_BINARY_DIR}/always-install.cmake
   )
-- 
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